Friday, April 2, 2010
A new study indicates that exposure to air pollution during any phase of the IVF process may have a negative impact on its success.
One common pollutant -- nitrogen dioxide (NO2), largely produced by vehicle exhaust -- was consistently linked to lower odds of IVF success. When NO2 levels were higher-than-average near a woman's home, or near the IVF lab, during any parts of the IVF process or during pregnancy, the chances of having a baby dipped.
The study, published in the journal Human Reproduction, included 7,403 women who underwent IVF at one of three fertility clinics between 2000 and 2007; the centers were located in Hershey, New York City and Rockville, Maryland, representing rural, urban and suburban areas.
Of the whole study group, 36 percent of the women had a baby following their first IVF treatment. Overall, Legro's team found that those odds dipped by 20 percent when the NO2 levels near a woman's home were 0.01 parts per million above average at the time she was taking medication to spur ovulation.
Similar effects were seen when the researchers focused on NO2 levels near the IVF center at the time of egg retrieval and fertilization, and levels near the women's homes after the embryos had been implanted. Although IVF labs are tightly controlled environments, their indoor air quality still varies, Legro said.
Still, while the study points to an association between air pollution, particularly NO2, and IVF outcomes, it does not prove cause-and-effect.
"We can't show a mechanism," Legro said. "We can't say that (for example,) poor air quality leads to poor egg quality."
And a key limitation of the study, he and his colleagues note, is that it did not have direct measurements of the women's personal exposure to various air pollutants.
"We still need to do further studies and confirm these findings," Legro said. "It's too soon to say what the ultimate effects (of air pollution) on reproduction are."
In theory, high levels of air pollutants could affect pregnancy outcomes for several reasons, according to Legro. Air pollution might cause widespread inflammation in the body, increase the body's production of cell-damaging oxygen-free radicals, or make the blood more prone to clotting -- all of which could pose a risk to pregnancy.
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